Artículos regulares in revistas
|Competition between dynamic and thermal relaxation in non-equilibrium critical spin systems above the critical point|
|Picone A., Henkel M., Richert J.|
|Journal of Physics A: Mathematical and General 36 (2003) 1249|
|ArXiv : cond-mat/0210330 [PDF]|
We study the long-time behaviour and the spatial correlations of a simple ferromagnetic spin system whose kinetics is governed by a thermal bath with a time-dependent temperature which is characterized by a given external relaxation time Ï". Exact results are obtained in the framework of the spherical model in d dimensions. In the paramagnetic phase, the long-time kinetics is shown to depend crucially on the ratio between Ï" and the internal equilibration time Ï"eq. If Ï" âo/oo² Ï" eq, the model relaxes rapidly towards an equilibrium state but there appear transient and spatially oscillating contributions in the spin-spin correlation function. On the other hand, if Ï" âo/oo« Ï"eq the system is clamped and its time evolution may be delayed with respect to that of the heat bath. For waiting times s such that Ï" âo/oo« s âo/oo« Ï" eq, a quasi-stationary state is found where the fluctuation-dissipation theorem does not hold.